The present invention relates to a stator structure and in particular to a stator structure for a motor and manufacturing method thereof.
A conventional fan is shown in FIG. 1 including a rotor assembly 1, a stator 2 and a frame 3. The rotor assembly 1 includes a blade structure 11 having a hub 111 and blades 112 disposed around the exterior periphery of the hub 111. A metal case 12 and a magnet 13 are disposed in the hub 111 accordingly. A shaft 113 is disposed in the center of the hub 111 and a washer 14 is placed on the shaft 113. The stator 2 includes a housing 21, a coil 22, an upper insulation spacer 23, an upper pole plate 24, a lower insulation spacer 25, a lower pole plate 26 and a circuit board 27. The housing 21 is a hollow tube and has bearing system therein. The upper insulation spacer 23 and the upper pole plate 24 are placed sequentially on top of coil 22, encircling the outer periphery of the housing 21. Next, the lower insulation spacer 25, the lower pole plate 26 and the circuit board 27 are placed sequentially, encircling the outer periphery of housing 21. Thus, the top surface of the lower insulation spacer 25 contacts the lower end of coil 22. The shaft 113 of the rotor assembly 1 passing through the opening in housing 21 is locked by a ring 116 connecting the rotor assembly 1 and the stator 2. A sensor is further disposed on the circuit board 27 to detect and control the magnetic field of the stator 2. Finally, the bottom surface of the stator 2 is connected to the frame 3 completing the fan assembly. Obviously, assembly of the stator 2 is complicated.
Another conventional stator is shown in FIG. 2. The stator includes upper and lower poles 28, a magnetically conductive bushing 29 and a coil 22. Each end of the magnetically conductive bushing 29 is securely engaged to the hollow portion of each pole 28. An insulator (not shown) sheathes the magnetically conductive bushing 29, and the coil 22 is wound around the insulator. During assembly, teeth 281 on each upper and lower pole 28 are positioned complementary to each other in order that each of the teeth 281 is spaced equally.
Another conventional stator structure is disclosed in U.S. Pat. No. 5,859,487, disclosing a stator structure is integrally formed by a hollow cogged plate having four short salients and four long salients, both connected to a ring, and four long salients bent to complete the stator structure, further comprising four pieces of waist posts. This stator structure is utilized in thin silicon steel to accommodate the bending procedure. Therefore, a magnetically conductive path is easily saturated, and the salients are too small to function efficiently.
Assembly of the conventional stator is complicated, time consuming, and requires accurate assembly as the relative positions of the pole and sensor are prone to deviation which reduces motor efficiency. In order to eliminate required matching of the upper and lower pole layers, a simple and stable stator structure for improving motor efficiency is called for.